Most commercial and military aircraft, as well as many civilian aircraft, carry flight data recorders (FDRs) or cockpit voice recorders (CVRs). During normal flight operations, the FDR records specific aircraft performance parameters, such as air speed, altitude, vertical acceleration, time, magnetic heading, control-column position, rudder-pedal position, control-wheel position, horizontal stabilizer, and fuel flow. The CVR records cockpit voices and other audio such as conversations between ground control and flight crew. The FDR and CVR have an enclosure containing electronic interface and processing circuits and a crash survivable memory unit (CSMU). The CSMU contains non-volatile memory for storing the flight data and voice data.
In the event of a crash, most of the flight recorder chassis and inner components may be damaged. However, the CSMU is designed to survive the impact, potential ensuing fire, and aftermath of various environmental conditions. For example, under the EUROCAE ED-112 standard, the flight recorder is required to withstand an impact of 3600 g and temperatures up to 1000° C. The data stored on the CSMU should still be recoverable.
Popularly known as the “black box” and regulated by International Civil Aviation Organization (ICAO), these units are crucial in investigating and understanding aircraft accidents. In fact, the recovery of the black box is second only to the recovery of survivors and victims. FDRs can also be used to study air safety issues, material degradation, unsafe flying procedures, and jet engine performance. The outer housing of the flight recorder is painted bright orange for ready identification and generally located in the tail section of the aircraft to maximize survivability.
The flight recorder receives electrical operating power from the main aircraft power bus. In an emergency condition, the main aircraft power bus may be disabled, which could cause loss of critical data in the moments before a crash. Accordingly, an auxiliary power supply is typically used to provide short term operating power for the flight recorder should the main aircraft power bus become disabled. The auxiliary power source is a separate unit which is wired to the flight recorder. U.S. Pat. No. 6,410,995 discloses this two-unit approach, i.e., CVR and separate auxiliary power supply.
The separate auxiliary power supply associated with prior art flight recorders has certain disadvantages. The FDR and CVR have specific dimensional space requirements imposed by various governing bodies. The separate auxiliary power supply requires additional space well beyond the dimensional specifications of the flight recorder itself. In addition, the two-unit approach (flight recorder and separate auxiliary power supply) increases maintenance, service, and replacement costs.